Mechanical Stimulation and IGF-1 Enhance mRNA Translation Rate in Osteoblasts Via Activation of the AKT-mTOR Pathway
| Autor: | Astrid D, Bakker, Tom, Gakes, Jolanda M A, Hogervorst, Gerard M J, de Wit, Jenneke, Klein-Nulend, Richard T, Jaspers |
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| Rok vydání: | 2015 |
| Předmět: |
Osteoblasts
Time Factors Dose-Response Relationship Drug TOR Serine-Threonine Kinases Cell Culture Techniques Ribosomal Protein S6 Kinases 70-kDa 3T3 Cells Mechanotransduction Cellular Enzyme Activation Mice Physical Stimulation Protein Biosynthesis Pulsatile Flow Animals RNA Messenger Insulin-Like Growth Factor I Phosphatidylinositol 3-Kinase Phosphorylation Protein Kinase Inhibitors Proto-Oncogene Proteins c-akt |
| Zdroj: | Journal of cellular physiology. 231(6) |
| ISSN: | 1097-4652 |
| Popis: | Insulin-like growth factor-1 (IGF-1) is anabolic for muscle by enhancing the rate of mRNA translation via activation of AKT and subsequent activation of the mammalian target of rapamycin complex 1 (mTOR), thereby increasing cellular protein production. IGF-1 is also anabolic for bone, but whether the mTOR pathway plays a role in the rate of bone matrix protein production by osteoblasts is unknown. We hypothesized that anabolic stimuli such as mechanical loading and IGF-1 stimulate protein synthesis in osteoblasts via activation of the AKT-mTOR pathway. MC3T3-E1 osteoblasts were either or not subjected for 1 h to mechanical loading by pulsating fluid flow (PFF) or treated with or without human recombinant IGF-1 (1-100 ng/ml) for 0.5-6 h, to determine phosphorylation of AKT and p70S6K (downstream of mTOR) by Western blot. After 4 days of culture with or without the mTOR inhibitor rapamycin, total protein, DNA, and gene expression were quantified. IGF-1 (100 ng/ml) reduced IGF-1 gene expression, although PFF enhanced IGF-1 expression. IGF-1 did not affect collagen-I gene expression. IGF-1 dose-dependently enhanced AKT and p70S6K phosphorylation at 2 and 6 h. PFF enhanced phosphorylation of AKT and p70S6K already within 1 h. Both IGF-1 and PFF enhanced total protein per cell by ∼30%, but not in the presence of rapamycin. Our results show that IGF-1 and PFF activate mTOR, thereby stimulating the rate of mRNA translation in osteoblasts. The known anabolic effect of mechanical loading and IGF-1 on bone may thus be partly explained by mTOR-mediated enhanced protein synthesis in osteoblasts. |
| Databáze: | OpenAIRE |
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